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Constitutive IP3 signaling underlies the sensitivity of B-cell cancers to the Bcl-2/IP3 receptor disruptor BIRD-2

Bittremieux, Mart; La Rovere, Rita M.; Akl, Haidar; Martines, Claudio; Welkenhuyzen, Kirsten; Dubron, Kathia; Baes, Myriam; Janssens, Ann; Vandenberghe, Peter; Laurenti, Luca; Rietdorf, Katja; Morciano, Giampaolo; Pinton, Paolo; Mikoshiba, Katsuhiko; Bootman, Martin D.; Efremov, Dimitar G.; De Smedt, Humbert; Parys, Jan B. and Bultynck, Geert (2018). Constitutive IP3 signaling underlies the sensitivity of B-cell cancers to the Bcl-2/IP3 receptor disruptor BIRD-2. Cell Death & Differentiation

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DOI (Digital Object Identifier) Link: https://doi.org/10.1038/s41418-018-0142-3
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Abstract

Anti-apoptotic Bcl-2 proteins are upregulated in different cancers, including diffuse large B-cell lymphoma (DLBCL) and chronic lymphocytic leukemia (CLL), enabling survival by inhibiting pro-apoptotic Bcl-2-family members and inositol 1,4,5-trisphosphate (IP3) receptor (IP3R)-mediated Ca2+-signaling. A peptide tool (Bcl-2/IP3R Disruptor-2; BIRD-2) was developed to abrogate the interaction of Bcl-2 with IP3Rs by targeting Bcl-2′s BH4 domain. BIRD-2 triggers cell death in primary CLL cells and in DLBCL cell lines. Particularly, DLBCL cells with high levels of IP3R2 were sensitive to BIRD-2. Here, we report that BIRD-2-induced cell death in DLBCL cells does not only depend on high IP3R2-expression levels, but also on constitutive IP3 signaling, downstream of the tonically active B-cell receptor. The basal Ca2+ level in SU-DHL-4 DLBCL cells was significantly elevated due to the constitutive IP3 production. This constitutive IP3 signaling fulfilled a pro-survival role, since inhibition of phospholipase C (PLC) using U73122 (2.5 µM) caused cell death in SU-DHL-4 cells. Milder inhibition of IP3 signaling using a lower U73122 concentration (1 µM) or expression of an IP3 sponge suppressed both BIRD-2-induced Ca2+ elevation and apoptosis in SU-DHL-4 cells. Basal PLC/IP3 signaling also fulfilled a pro-survival role in other DLBCL cell lines, including Karpas 422, RI-1 and SU-DHL-6 cells, whereas PLC inhibition protected these cells against BIRD-2-evoked apoptosis. Finally, U73122 treatment also suppressed BIRD-2-induced cell death in primary CLL, both in unsupported systems and in co-cultures with CD40L-expressing fibroblasts. Thus, constitutive IP3 signaling in lymphoma and leukemia cells is not only important for cancer cell survival, but also represents a vulnerability, rendering cancer cells dependent on Bcl-2 to limit IP3R activity. BIRD-2 seems to switch constitutive IP3 signaling from pro-survival into pro-death, presenting a plausible therapeutic strategy.

Item Type: Journal Item
Copyright Holders: 2018 The Authors
ISSN: 1350-9047
Project Funding Details:
Funded Project NameProject IDFunding Body
Not SetG.0571.12 NFund for Scientific Research-Flanders (FWO)
Not SetG.0634.13 NFund for Scientific Research-Flanders (FWO)
Not SetG.0C91.14 NFund for Scientific Research-Flanders (FWO)
Not SetG.0A34.16 NFund for Scientific Research-Flanders (FWO)
Not SetOT14/101Research Council-KU Leuven
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Life, Health and Chemical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 55556
Depositing User: Martin Bootman
Date Deposited: 22 Jun 2018 09:44
Last Modified: 14 Sep 2018 21:45
URI: http://oro.open.ac.uk/id/eprint/55556
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